PWM controller integrates key PSU components

New from Semtech, the SC1104 is a highly integrated synchronous voltage-mode PWM controller.

New from Semtech, the SC1104 is a highly integrated synchronous voltage-mode PWM controller.

The SC1104 lends itself to the design of single-ended DC/DC power supplies where key priorities are small circuit-board space and high efficiency.

Working as a buck regulator for reducing input voltages between +4.5 and +13V to output voltages as low as 1V, the SC1104 is well suited to telecommunications, networking, and data processing equipment, serving as the central component for building low-cost point-of-load power supplies for microprocessors, peripheral cards, and industrial devices drawing load currents of up to 10A.

By sweeping several key functional blocks onto one chip in a SO-8 package, the SC1104 minimises the number of components needed to build an efficient low-voltage power supply.

Specifically embodied in the SC1104 are level shifting and 1A gate-drive circuitry, precluding the need for a costly P-channel, high-side FET switch; temperature-compensated, 1%-accurate voltage reference; externally compensated error amplifier; triangle-wave oscillator; and current-limit comparator.

By reducing overall component count, the SC1104 not only conserves limited circuit-board space, it also cuts overall product cost and improves reliability.

"Present day DC/DC power supplies demand ever greater efficiencies, smaller footprints, and lower costs", notes George Georgalis, Semtech's Director of Telecom and Industrial Power Management.

"The SC1104 adds a versatile, compact, and highly efficient synchronous voltage-mode PWM controller to Semtech's portfolio, giving telecomms, datacomms and industrial equipment designers an important component for building high-density, single-ended, DC/DC power management systems".

The SC1104 is available in versions with fixed (and therefore easy to filter) switching frequencies of 300 and 600kHz.

The choice of switching frequencies gives designers an added option for balancing efficiency, external component size, and cost to meet overall system needs.

Specifically, 300kHz operation gives the highest efficiency, up to 95%, but requires slightly larger components than the 600kHz version.

Alternatively, the smallest possible footprint is achieved by designing in the 600kHz version, which is intended for use with a 5V input.

Other noteworthy features of the SC1104 include its externally adjustable, hiccup-mode RDS(on) overcurrent protection; automatic thermal shutdown; undervoltage lockout; and soft start turn on to prevent current surges during power up.

The SC1104 maintains a better than 2% voltage regulation over specified line voltage, load current, and temperature variations.

The SC1104 comes in a SO-8 package and is rated to operate over the industrial temperature range of -40 to +125C.

Prices start at $1.20 each in quantities of 10,000+.

An evaluation board (SC1104EVB) is also available.

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